Low-E panels with ternary metal oxide dielectric layer and method for forming the same

ABSTRACT

Embodiments provided herein describe a low-e panel and a method for forming a low-e panel. A transparent substrate is provided. A metal oxide layer is formed over the transparent substrate. The metal oxide layer includes a first element, a second element, and a third element. A reflective layer is formed over the transparent substrate. The first element may include tin or zinc. The second element and the third element may each include tin, zinc, antimony, silicon, strontium, titanium, niobium, zirconium, magnesium, aluminum, yttrium, lanthanum, hafnium, or bismuth. The metal oxide layer may also include nitrogen.

The present invention relates to low-e panels. More particularly, thisinvention relates to low-e panels having a ternary metal oxidedielectric layer and a method for forming such low-e panels.

BACKGROUND OF THE INVENTION

Low emissivity, or low-e, panels (e.g., low-e glass panels) are oftenformed by depositing a reflective layer (e.g., silver), along withvarious other layers, onto a transparent substrate, such as glass. Thevarious layers typically include dielectric layers, such as siliconnitride, tin oxide, and zinc oxide, to provide a barrier between thestack and both the glass and the environment.

Conventional low-e panels using such dielectric layers often form cracksalong grain boundaries, especially in applications where the glass isbent or otherwise shaped. Additionally, conventional low-e panels oftendemonstrate significant changes in color during heat treatment (ortempering) after the layers (i.e., the stack) are formed on the glass.As such, the tempered panels appear to have a different color than thosethat have not been tempered.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings:

FIG. 1 is a cross-sectional side view of a low-e panel according to oneembodiment of the present invention.

FIG. 2 is a simplified cross-sectional diagram illustrating a physicalvapor deposition (PVD) tool according to one embodiment of the presentinvention.

DETAILED DESCRIPTION

A detailed description of one or more embodiments is provided belowalong with accompanying figures. The detailed description is provided inconnection with such embodiments, but is not limited to any particularexample. The scope is limited only by the claims and numerousalternatives, modifications, and equivalents are encompassed. Numerousspecific details are set forth in the following description in order toprovide a thorough understanding. These details are provided for thepurpose of example and the described techniques may be practicedaccording to the claims without some or all of these specific details.For the purpose of clarity, technical material that is known in thetechnical fields related to the embodiments has not been described indetail to avoid unnecessarily obscuring the description.

Embodiments described herein provide low-e panels with improvedstructural reliability and improved optical property stability.According to one aspect, a ternary metal oxide (or oxynitride)dielectric is used in the low-e stack. The ternary oxide is, forexample, based on tin oxide or zinc oxide, and includes an additionaltwo elements (i.e., for a total of three elements in addition to theoxygen and/or nitrogen). Examples of the additional elements includetin, zinc, antimony, silicon, strontium, titanium, niobium, zirconium,magnesium, aluminum, yttrium, lanthanum, hafnium, and bismuth. However,the three elements are unique (i.e., the metal is different than the twoadditional elements and the two additional elements are different fromeach other). Nitrogen gas may also be introduced during the formation ofthe dielectric such that the layer is a metal oxynitride.

The resulting dielectric layer forms an amorphous phase and demonstratesimproved structural and optical stability after subsequent processes,such as heat treatments, compared to conventional tin oxide and zincoxide dielectrics. The amorphous phase reduces grain boundaries that aresusceptible to cracking in conventional low-e panels. As a result, low-epanels described herein may be bent and shaped without any crackingoccurring along grain boundaries.

Additionally, the stability of the optical properties of the panelsdescribed herein is improved when compared to conventional panels.Specifically, changes in optical properties, such as refractive index(n) and extinction coefficient (k), caused by heat treatment arereduced, as are changes in overall color.

Further, the addition of nitrogen (i.e., the use of a ternary metaloxynitride), reduces the energy state of the material, thus providing astable barrier against sodium diffusion, as well as moisture and air inthe environment.

In one embodiment, a method for forming a low-e panel is provided. Atransparent substrate is provided. A metal oxide layer is formed overthe transparent substrate. The metal oxide layer includes oxygen, afirst element, a second element, and a third element. A reflective layeris formed over the transparent substrate. The first element may includetin or zinc. The second element and the third element may each includetin, zinc, antimony, silicon, strontium, titanium, niobium, zirconium,magnesium, aluminum, yttrium, lanthanum, hafnium, or bismuth.

FIG. 1 illustrates a low-e panel 10 according to one embodiment of thepresent invention. The low-e panel 10 includes a transparent substrate12 and a low-e stack 14 formed over the transparent substrate 12. Thetransparent substrate 12 in one embodiment is made of a low emissivityglass, such as borosilicate glass. However, in other embodiments, thetransparent substrate 12 may be made of plastic or polycarbonate. Thesubstrate 12 has a thickness of, for example, between 1 and 10millimeters (mm). In a testing environment, the transparent substrate 12may be round with a diameter of, for example, 200 or 300 mm. However, ina manufacturing environment, the substrate 12 may be square orrectangular and significantly larger (e.g., 0.5-6.0 meters (m) across).

The low-e stack 14 includes a lower dielectric layer 16, a lower metaloxide layer 18, a reflective layer 20, a metal alloy layer 22, an uppermetal oxide layer 24, an upper dielectric layer 26, and a protectivelayer 28. Exemplary details as to the functionality provided by each ofthe layers 16-28 are provided below.

The various layers in the low-e stack 14 may be formed sequentially(i.e., from bottom to top) on the transparent substrate 12 using aphysical vapor deposition (PVD) and/or reactive (or plasma enhanced)sputtering processing tool. In one embodiment, the low-e stack 14 isformed over the entire substrate 12. However, in other embodiments, thelow-e stack 14 may only be formed on isolated portions of the substrate12.

Still referring to FIG. 1, the lower dielectric layer 16 is formed onthe upper surface of the transparent substrate 12. In one embodiment,the lower dielectric layer 16 is made of a ternary metal oxide or aternary metal oxynitride. That is, the lower dielectric layer 16 may bemade of a metal oxide or a metal oxynitride that includes three elementsin additional to oxygen and/or nitrogen: a baseline metal and twoadditional elements.

The baseline metal, or first element, may be tin, zinc, or a combinationthereof. In one embodiment, the first element accounts for between 15%and 92% by weight of the material of the lower dielectric layer 16.

The second element may be selected from a group that forms a compoundwith the baseline metal, such as tin, zinc, antimony, silicon,strontium, titanium, niobium, or zirconium, which may account forbetween 35% and 55% by weight of the material of the lower dielectriclayer 16. Alternatively, the second element may be selected from a groupof elements that form amorphous oxides when reactively sputtered withoxygen, such as magnesium, aluminum, yttrium, lanthanum, or hafnium,which may account for between 3% and 35% by weight of the material ofthe lower dielectric layer 16.

The third element may be selected from the same groups of elements fromwhich the second element is chosen. However, bismuth may also be used.Thus, the third element may be selected from tin, zinc, antimony,silicon, strontium, titanium, niobium, zirconium, magnesium, aluminum,yttrium, lanthanum, hafnium, or bismuth. The third element may accountfor between 3% and 35% by weight of the material of the lower dielectriclayer 16. The third element is preferably an element with a mid to highrefractive index, such as titanium, antimony, bismuth, and niobium.

However, it should be understood that in at least some embodiments,three different or unique elements are used. That is, the first elementis different than the second and third elements, and the second elementis different than the third element. In one embodiment, the lowerdielectric layer 16 is zinc-tin-titanium oxide.

It should be understood that the three elements may be deposited usingvarious numbers of targets in, for example, a PVD tool, an example ofwhich is described below. For example, each of the elements may beejected from a separate target unique to (i.e., made of) that particularelement. Alternatively, the elements may be deposited using alloytargets that include two, or more, of the elements, such as zinc, tin,and titanium. Further, the lower dielectric layer 16 may be made intothe ternary oxynitride by, for example, using targets that includeoxygen and nitrogen, or by introducing nitrogen into, for example, thePVD chamber, along with oxygen, when using a reactive sputteringtechnique.

As described above, the resulting lower dielectric layer 16 has, whencompared to prior art dielectrics, a reduced number of grain boundariesand demonstrates improved optical stability.

The lower dielectric layer 16 has a thickness of, for example, 250Angstroms (Å). The lower dielectric layer 16 may protect the otherlayers in the stack 14 from any elements which may otherwise diffusefrom the substrate 12 and may be used to tune the optical properties(e.g., transmission) of the stack 14 and/or the low-e panel 10 as awhole. For example, the thickness and refractive index of the lowerdielectric layer 16 may be used to increase or decrease visible lighttransmission.

The lower metal oxide layer 18 is formed over the substrate 12 and onthe lower dielectric layer 16. In one embodiment, the lower metal oxidelayer 18 is made of as zinc oxide and has a thickness of, for example,100 Å. The lower metal oxide layer 18 may enhance the texturing of thereflective layer 20 and increase the transmission of the stack 14 foranti-reflection purposes. It should be understood that in otherembodiments, the lower metal oxide layer 18 may be made of tin oxide ormay not be included at all.

Referring again to FIG. 1, in the depicted embodiment, the reflectivelayer 20 is formed on the lower metal oxide layer 18. In one embodiment,the reflective layer 20 is made of silver and has a thickness of, forexample, 100 Å.

Still referring to FIG. 1, the metal alloy layer 22 and the upper metaloxide layer 24 are formed over the reflective layer 20. In oneembodiment, the metal alloy layer 24 is made of nickel-chromium and hasa thickness of, for example, 30 Å. The metal alloy layer 22 may preventthe reflective layer 20 from oxidizing and protect the reflective layer20 during subsequent processing steps, such as heating. The upper metaloxide layer 24 is formed on the metal alloy layer 24. In one embodiment,the upper metal oxide layer 24 includes the metal alloy of the metalalloy layer 22 (e.g., nickel-chromium oxide) and has a thickness of, forexample, 30 Å. The upper metal oxide layer 24 may provide adhesionbetween the reflective layer 20 and the upper dielectric layer 26.

The upper dielectric layer 26 is formed on the upper metal oxide layer24. In one embodiment, the upper dielectric layer 26 is made of the samematerial as the lower dielectric layer 16 (e.g., a ternary metal oxideor a ternary metal oxynitride). That is, the material of the upperdielectric layer 26 may include three elements (i.e. a fourth element, afifth element, and a sixth element) that are the same as the threerespective elements (i.e., the first element, the second element, andthe third element) in the material of the lower dielectric layer 16. Thelower dielectric layer may have the same thickness as the lowerdielectric layer 16 and may be used for anti-reflection purposes, aswell as a barrier against the environment.

Still referring to FIG. 1, the protective layer 28 is formed on theupper dielectric layer 26. In one embodiment, the protective layer 28 ismade of silicon nitride and has a thickness of, for example, 250 Å. Theprotective layer 28 may be used to provide additional protection for thelower layers of the stack 14 and further adjust the optical propertiesof the stack 14. However, it should be understood that some embodimentsmay not include the protective layer 28. Additionally, although notshown in FIG. 1, some embodiments may also include a second protectivelayer (e.g., silicon nitride) between the glass substrate 12 and thelower dielectric layer 16.

It should be noted that depending on the exact materials used, some ofthe layers of the low-e stack 14 may have some materials in common. Anexample of such a stack may use a zinc-based material in the dielectriclayers 16 and 26 and include a zinc oxide lower metal oxide layer 18. Asa result, embodiments described herein may allow for a relatively lownumber of different targets to be used for the formation of the low-estack 14. This is particularly true for embodiments that do not includethe protective layer 28.

Thus, in some embodiments, a method for forming a low-e panel isprovided. A transparent substrate is provided. A metal oxide layer isformed over the transparent substrate. The metal oxide layer includesoxygen, a first element, a second element, and a third element. Thefirst element is different than the second element and the thirdelement, and the second element is different than the third element. Thefirst element includes tin or zinc. The second element and the thirdelement each include tin, zinc, antimony, silicon, strontium, titanium,niobium, zirconium, magnesium, aluminum, yttrium, lanthanum, hafnium, orbismuth. A reflective layer is formed over the transparent substrate.

In another embodiment, a low-e panel is provided. The low-e panelincludes a transparent substrate, a metal oxide layer formed over thetransparent substrate, and a reflective layer formed over the metaloxide layer. The metal oxide layer includes oxygen, a first element, asecond element, and a third element. The first element is different thanthe second element and the third element, and the second element isdifferent than the third element. The first element includes tin orzinc. The second element and the third element each include tin, zinc,antimony, silicon, strontium, titanium, niobium, zirconium, magnesium,aluminum, yttrium, lanthanum, hafnium, or bismuth.

In a further embodiment, a method for forming a low-e panel is provided.A transparent substrate is provided. A metal oxynitride layer is formedover the transparent substrate. The metal oxynitride layer includes afirst element, a second element, and a third element. The first elementis different than the second element and the third element, and thesecond element is different than the third element. The first elementincludes tin or zinc. The second element includes tin, zinc, antimony,silicon, strontium, titanium, niobium, zirconium, magnesium, aluminum,yttrium, lanthanum, or hafnium. The third element includes titanium,antimony, bismuth, or niobium. A silver layer is formed over thetransparent substrate.

FIG. 2 provides a simplified illustration of a physical vapor deposition(PVD) tool (and/or system) 200 which may be used to formed the low-eglass panel 10 and/or the low-e stack 14 described above, in accordancewith one embodiment of the invention. The PVD tool 200 shown in FIG. 2includes a housing 202 that defines, or encloses, a processing chamber204, a substrate support 206, a first target assembly 208, and a secondtarget assembly 210.

The housing 202 includes a gas inlet 212 and a gas outlet 214 near alower region thereof on opposing sides of the substrate support 206. Thesubstrate support 206 is positioned near the lower region of the housing202 and in configured to support a substrate 216. The substrate 216 maybe a round glass (e.g., borosilicate glass) substrate having a diameterof, for example, 200 mm or 300 mm. In other embodiments (such as in amanufacturing environment), the substrate 216 may have other shapes,such as square or rectangular, and may be significantly larger (e.g.,0.5-6 m across). The substrate support 206 includes a support electrode218 and is held at ground potential during processing, as indicated.

The first and second target assemblies (or process heads) 208 and 210are suspended from an upper region of the housing 202 within theprocessing chamber 204. The first target assembly 208 includes a firsttarget 220 and a first target electrode 222, and the second targetassembly 210 includes a second target 224 and a second target electrode226. As shown, the first target 220 and the second target 224 areoriented or directed towards the substrate 216. As is commonlyunderstood, the first target 220 and the second target 224 include oneor more materials that are to be used to deposit a layer of material 228on the upper surface of the substrate 216.

The materials used in the targets 220 and 224 may, for example, includetin, zinc, antimony, silicon, strontium, titanium, niobium, zirconium,magnesium, aluminum, yttrium, lanthanum, hafnium, bismuth, silicon,silver, nickel, chromium, or any combination thereof (i.e., a singletarget may be made of an alloy of several metals). Additionally, thematerials used in the targets may include oxygen, nitrogen, or acombination of oxygen and nitrogen in order to form the oxides,nitrides, and oxynitrides described above. Additionally, although onlytwo targets 220 and 224 are shown in the depicted embodiment, additionaltargets may be used. As such, different combinations of targets may beused to form, for example, the dielectric layers described above. Forexample, in an embodiment in which the dielectric material iszinc-tin-titanium oxide, the zinc, the tin, and the titanium may beprovided by separate zinc, tin, and titanium targets, or they may beprovided by a single zinc-tin-titanium alloy target.

The PVD tool 200 also includes a first power supply 230 coupled to thefirst target electrode 222 and a second power supply 232 coupled to thesecond target electrode 224. As is commonly understood, the powersupplies 230 and 232 pulse direct current (DC) power to the respectiveelectrodes, causing material to be, at least in some embodiments,simultaneously sputtered (i.e., co-sputtered) from the first and secondtargets 220 and 224.

During sputtering, inert gases, such as argon or kypton, may beintroduced into the processing chamber 204 through the gas inlet 212,while a vacuum is applied to the gas outlet 214. However, in embodimentsin which reactive sputtering is used, reactive gases may also beintroduced, such as oxygen and/or nitrogen, which interact withparticles ejected from the targets (i.e., to form oxides, nitrides,and/or oxynitrides).

Although not shown in FIG. 2, the PVD tool 200 may also include acontrol system having, for example, a processor and a memory, which isin operable communication with the other components shown in FIG. 2 andconfigured to control the operation thereof in order to perform themethods described herein.

Further, although the PVD tool 200 shown in FIG. 2 includes a stationarysubstrate support 206, it should be understood that in a manufacturingenvironment, the substrate 216 may be in motion during the variouslayers described herein.

Although the foregoing examples have been described in some detail forpurposes of clarity of understanding, the invention is not limited tothe details provided. There are many alternative ways of implementingthe invention. The disclosed examples are illustrative and notrestrictive.

What is claimed:
 1. A low-e panel comprising: a transparent substrate; ametal oxide layer formed over the transparent substrate, wherein themetal oxide layer comprises oxygen, a first element, a second element,and a third element, wherein the first element is tin or zinc, thesecond element is strontium, and the third element is hafnium; and areflective layer formed over the transparent substrate.
 2. The low-epanel of claim 1, wherein the metal oxide layer further comprisesnitrogen, and the reflective layer is formed over the metal oxide layer.3. The low-e panel of claim 2, further comprising a second metal oxidelayer formed over the reflective layer, the second metal oxide layercomprising a fourth element, a fifth element, and a sixth element,wherein the fourth element is tin or zinc, the fifth element isstrontium, and the sixth element is hafnium.
 4. The low-e panel of claim3, wherein the first element is the same as the fourth element, thesecond element is the same as the fifth element, and the third elementis the same as the sixth element, and wherein the second the metal oxidelayer further comprises nitrogen.
 5. The low-e panel of claim 1, whereinthe reflective layer comprises silver.
 6. A low-e panel comprising: atransparent substrate; a first metal oxide layer formed over thetransparent substrate, wherein the first metal oxide layer comprisesoxygen, a first element, a second element, and a third element, whereinthe first element is tin or zinc, the second element is strontium, andthe third element is hafnium; a reflective layer formed over the firstmetal oxide layer; and a second metal oxide layer formed over thereflective layer, wherein the second metal oxide layer is made of thesame material as the first metal oxide layer.
 7. The low-e panel ofclaim 6, wherein the first metal oxide layer further comprises nitrogen.8. The low-e panel of claim 7, wherein the reflective layer comprisessilver.
 9. A low-e panel comprising: a transparent substrate; a metaloxide layer formed over the transparent substrate, wherein the metaloxide layer consists of oxygen, a first element, a second element, and athird element, wherein the first element is different than the secondelement and the third element, and wherein the second element isdifferent than the third element, and wherein the first element is tin,and the second element and the third element are each selected from thegroup consisting of strontium, magnesium, and hafnium; and a reflectivelayer formed over the transparent substrate.
 10. The low-e panel ofclaim 9, wherein the reflective layer is formed over the metal oxidelayer.
 11. The low-e panel of claim 10, further comprising a secondmetal oxide layer formed over the reflective layer, wherein the secondmetal oxide layer consists of oxygen, a fourth element, a fifth element,and a sixth element, wherein the fourth element is different than thefifth element and the sixth element, and wherein the fifth element isdifferent than the sixth element, and wherein the fourth element is tin,and the fifth element and the sixth element are each selected from thegroup consisting of strontium, magnesium, and hafnium.